The present invention relates to a method of mounting a variety of electronic components requiring different levels of mounting accuracy on a substrate, and an apparatus for mounting the same.
Apparatuses for mounting electronic components widely available now are the types that mount electronic components on substrates by picking up the electronic components provided in a part feeder such as a tape feeder, a tubular feeder, a bulk feeder, a tray feeder, and the like, with a nozzle on a transfer head with vacuum suction, and moving the transfer head horizontally with an X table and a Y table.
Because an electronic component picked up by the nozzle is deviated in position, the apparatus determines a position of the electronic component with a recognition device prior to mounting the electronic component on the substrate. An optical device such as a camera with an area type CCD, a camera with a line type CCD, and the like, for observing information related to a plane, or an optical device such as laser unit for observing height information are used for the recognition device.
FIG. 6 is a plan view depicting moving loci of a transfer head of a conventional apparatus for mounting electronic components where such apparatus is provided with a line sensor for the recognition device. In the figure, a substrate 1 is set in a position on guide rails 2. A tray feeder 3 provided with two trays 3a is placed on one side of the substrate 1, and a plurality of tape feeders 4 and bulk feeders 5 are placed on the other side of the substrate 1. Also, a recognition device 6 is provided between the substrate 1 and the tray feeder 3. The recognition device is equipped with a line sensor.
The transfer head (not shown in the figure) transfers and mounts an electronic component on the substrate 1, after picking up the electronic component from the tray feeder 3, the tape feeder 4 or the bulk feeder 5 with the nozzle on the transfer head with vacuum suction, and after determining a position of the electronic component being vacuum-chucked on a lower tip of the nozzle by moving the component over the recognition device 6.
In the figure, a polygonal line A with an arrow (hereinafter called an xe2x80x9carrow Axe2x80x9d) is a moving locus of the transfer head, when it mounts on the substrate 1 an electronic component picked up from the tray 3a on the left side of the tray feeder 3. Similarly, arrows B, C and D are moving loci of the transfer head for mounting on the substrate 1 electronic components from the tray 3a on the right side of the tray feeder 3, the tape feeder 4, and the bulk feeder 5, respectively. In order for the apparatus to discern an electronic component, it moves the transfer head over the line sensor in a direction orthogonal to a longitudinal direction of the line sensor (an X direction in FIG. 6), and obtains plane information of the electronic component by scanning it.
In FIG. 6, the apparatus discerns an electronic component while moving the transfer head, which carries the electronic component picked up from the tray 3a on the left side, to the rightward direction (an X1 direction) as shown by the arrow A. Likewise, the apparatus discerns an electronic component while moving the transfer head which carries the electronic component picked up from the tray 3a on the right side, to the leftward direction (an X2 direction) as shown by the arrow B.
In the case of a line sensor, however, an error (a positional deviation) of one or more picture elements occurs in the data obtained for a position of the electronic component due to the direction of scanning (whether in the X1 direction or the X2 direction). It is considered that this positional deviation may be caused by a difference in flow speed of the signal output from the line sensor existing between directions of the scanning. If an error occurs in the positional data of the electronic component due to the direction of scanning, accuracy of the mounting position can not be maintained, since a preciseness of the position where the electronic component is mounted on the substrate 1 will also deviate.
Since the tray feeder normally carries certain electronic components such as QFPs that require a high accuracy for the mounting position, a positional deviation of one or more picture elements as described above can not be disregarded in the case of such electronic components. On the contrary, mounting accuracy required for electronic components provided in the tape feeder and the bulk feeder is not so high. Therefore, in general, the positional deviation as described above can practically be ignored.
Accordingly, an object of the present invention is to provide a method and an apparatus for mounting electronic components that can mount the electronic components requiring a high accuracy of the mounting position on a substrate according to the required high positional accuracy by eliminating an error in the discerned position due to scanning direction of the line sensor, when mounting a variety of electronic components requiring different levels of the mounting accuracy on the substrate.
A method of mounting electronic components of the present invention includes picking up an electronic component requiring a higher accuracy of mounting position and an electronic component requiring a lower accuracy of mounting position provided in part feeders with an electronic component pickup unit mounted on a transfer head. Next, a position of only the electronic component requiring a higher accuracy of mounting position among the electronic components picked up by the electronic component pickup unit is discerned by moving the electronic component over a line sensor unidirectionally in a fixed direction orthogonal to a longitudinal direction of the line sensor. Then, the electronic component picked up by the electronic component pickup unit is mounted on a substrate based on a discerned result of the position of the electronic component.
Since this mounting method obtains image data by moving the electronic component requiring a higher accuracy of mounting position only in a fixed direction over the line sensor, it eliminates a variance in discerning accuracy of the position due to a difference caused by the scanning direction with respect to the line sensor, so as to enable mounting of the electronic component on the substrate with a high accuracy in the mounting position.
Also, a calibration of a nozzle on the transfer head to be executed prior to mounting the electronic component is performed preferably in the same direction as the above scanning direction.
Further, an electronic-component mounting apparatus of the present invention includes a recognition device provided with a line sensor for discerning a position of an electronic component moving above the line sensor in a direction orthogonal to a longitudinal direction of the line sensor, and a part feeder placed on one side of the recognition device with respect to a direction orthogonal to the longitudinal direction of the line sensor in the recognition device, for storing electronic components requiring a higher accuracy of mounting position. The apparatus also includes a part feeder for storing electronic components requiring a lower accuracy of mounting position, and a transfer head provided with a pickup unit for picking up an electronic component from the part feeder which stores electronic components requiring a higher accuracy of mounting position and from the part feeder which stores electronic components requiring a lower accuracy of mounting position.
Since the apparatus of the foregoing structure is able to obtain image data by moving the electronic component requiring a higher accuracy of mounting position only in one fixed direction over the line sensor at all times, it can mount the electronic component on the substrate with a high accuracy in the mounting position.